To provide an Italian language input system requiring less frequent key pressing.

In a three-row five-column input keyboard, by having some keys thereof take charge of inputting of a plurality of consonants or a plurality of vowels, it is made possible to divide formally all letters of the alphabet into a consonant keyboard and a vowel keyboard. Positioning on the vowel keyboard ten pairs of diphthongs higher in appearance frequency in word spelling, in addition to five basic vowels, and an input system of having these two keyboards automatically replace with each other in response to an input is adopted, the plurality of consonants and vowels are simultaneously inputted by pressing down the corresponding keys once each, and the result of inputting is finalized by comparing it with a database made ready in advance. In inputting consecutive consonants and consecutive vowels, by temporarily cancelling the automatic keyboard replacement by inputting preceding letters of the alphabet by keeping the keys pressed slightly longer than usual, inputting can be accomplished by a frequency of key pressing close to the frequency a currently personal computer would require to input the same content.